1. Field of the Invention
The present invention relates to a lapping method of a magnetic head slider with a magnetoresistive effect (MR) element, used in a magnetic disk drive apparatus or a hard disk drive (HDD) for example, and to a lapping method of a bar provided with a plurality of aligned magnetic head sliders.
2. Description of the Related Art
Recently, a read/write track width of a thin-film magnetic head has become very narrow to satisfy the requirement for ever increasing data storage capacities and densities in today""s magnetic disk drive apparatus. Then, it has become necessary to fabricate an MR element such as an anisotropic magnetoresistive effect (AMR) element or a giant magnetoresistive effect (GMR) element with a narrower track width and a shorter MR height. More specifically, MR elements with a very short MR height of about 0.2-0.15 xcexcm will be mass-produced in the near future.
Such shortening in MR height has sometimes induced characteristic degradation of the MR element when the air bearing surface (ABS) of the magnetic head slider is finished or lapped. Hereinafter, this problem which has occurred in the recent MR element will be described in detail.
The MR element with an extremely short MR height has inherently a very narrowed shield gap. For example, the total thickness in upper and lower shield gap layers of a recent MR element is as small as 0.1 xcexcm or less. The MR characteristics of the MR element with very thin shield gaps is susceptible to fine scratches formed on the ABS of the slider when lapping. Particularly, the MR element with an MR height of 0.3 xcexcm or less is extremely susceptible to such fine scratches on the ABS.
In general, the ABS of a magnetic head slider with an MR element is lapped by using diamond abrasive with a particle diameter of about 0.1-0.5 xcexcm, and thus fine scratches as a result of the abrasive will be formed on the lapped surface. A roughness of the element surface after lapping will be about Ra=0.3-1.0 nm. These fine scratches will, depending upon its running directions, namely lapped directions, greatly degrade the output characteristics of the MR element.
FIG. 1 illustrates lapping directions viewed from the ABS, in a conventional ABS finishing process of a magnetic head slider, and FIG. 2 shows a plane view of an MR element section viewed from the ABS, for illustrating problems occurring in the conventional ABS finishing process.
In these figures, reference numeral 10 denotes a lower shield layer of the MR element, 11 denotes an upper shield layer of the MR element, which also serves as a lower pole layer of an inductive element, 12 denotes an upper pole layer of the inductive element, and 13 denotes lapped directions, respectively. As shown in FIG. 2, an upper shield gap layer 14 and a lower shield gap layer 15 are inserted between the upper and lower shield layers 10 and 11, and between these upper and lower shield gap layers 14 and 15, an MR layer 16 and lead conductor layers 17 and 18 for this MR layer 16 are inserted.
According to this finishing method, because a bar consisting of a plurality of magnetic head sliders continuously coupled and aligned is lapped by turning itself with respect to a rotating lapping plate, the lapped directions 13 become random, as shown in FIG. 1, and thus scratches run along random directions. As a result, metal material is drawn from metal layers such as the lower shield layer 10, the upper shield layer 11, the lead conductor layer 17 and/or the lead conductor layer 18 as a result of the scratches causing smears 19 to be produced.
If the shield gap layers are sufficiently thick, as in the conventional MR element, these smears 19 become insignificant. However, in case of a recent MR element having extremely thin shield gap layers, these smears 19 will make short circuits to reduce an apparent resistance of the MR element and also to degrade MR conversion characteristics of the MR element, namely to reduce a peak to peak (PP) voltage output from the MR element in response to an applied alternating magnetic field.
FIG. 3 illustrates lapping directions viewed from the ABS, in another ABS finishing process of a magnetic head slider, implemented by the applicant so as to solve the above-mentioned problems, and FIG. 4 shows a plane view of an MR element section viewed from the ABS, for illustrating problems occurring in the applicant""s ABS finishing process.
In these figures, reference numeral 30 denotes a lower shield layer of the MR element, 31 denotes an upper shield layer of the MR element, which also serves as a lower pole layer of an inductive element, 32 denotes an upper pole layer of the inductive element, and 33 denotes lapped directions, respectively. As shown in FIG. 4, an upper shield gap layer 34 and a lower shield gap layer 35 are inserted between the upper and lower shield layers 30 and 31, and between these upper and lower shield gap layers 34 and 35, an MR layer 36 and lead conductor layers 37 and 38 for this MR layer 36 are inserted.
According to this finishing method, because a bar consisting of a plurality of magnetic head sliders continuously coupled and aligned is lapped by relatively moving the bar with respect to a lapping plate in a direction along the element-forming surface of the bar, the lapped direction 33 becomes parallel with the lower shield layer 30 and the upper shield layer 31 as shown in FIG. 3 and thus scratches run along the same direction.
This latter finishing method can prevent an apparent resistance of the MR element from being reduced even if the MR element has extremely thin shield gap layers. However, degradation in MR conversion characteristics of the MR element will occur. The reasons for this are that (1) because the lead conductor layers 37 and 38 are drawn as a result of the scratches as shown in FIG. 4, smears 39 parallel to the lower shield layer 30 and the upper shield layer 31 are produced to shorten an effective track width of the MR element, and that (2) because of mechanical stress applied to the MR layer 36 as a result of the lapping, a part of this MR layer is altered causing loss of MR conversion function of this part.
It is therefore an object of the present invention to provide a lapping method of a magnetic head slider and a lapping method of a bar, whereby degradations in both resistance and MR conversion characteristics of an MR element can be prevented.
According to the present invention, a lapping method of a magnetic head slider provided with an element-forming surface, an ABS and an MR element formed on the element-forming surface, includes a step of setting the magnetic head slider to be lapped on a lapping means, and a step of lapping by the lapping means the ABS of the magnetic head slider while keeping an angle between the element-forming surface of the magnetic head slider and a lapping direction in a range greater than 0 degrees and equal to or less than 30 degrees.
The ABS is lapped under the conditions where an angle between the element-forming surface of the magnetic head slider, namely, a shield gap layer of the MR element of the magnetic head slider and a lapping direction is kept in a range greater than 0 degrees and equal to or less than 30 degrees. Thus, not only lowering in a resistance of the MR element but also degradation in MR conversion characteristics of the MR element can be prevented.
It is preferred that the lapping direction is a direction from a side of a surface of the magnetic head slider, which surface is opposite the element-forming surface, toward a side of the element-forming surface.
According to the present invention, also, a lapping method of a bar having a plurality of aligned magnetic head sliders, the bar provided with an element-forming surface, an ABS and a plurality of MR elements formed on the element-forming surface includes a step of contacting the bar to be lapped to a rotating lapping plate while keeping an angle xcex8 between the element-forming surface of the bar and a radial direction of the rotating lapping plate in a range equal to or greater than 60 degrees and equal to or less than 80 degrees, and a step of lapping by the rotating lapping plate the ABS of the bar.
The ABS of the bar is contacted to the lapping plate and lapped under the conditions where an angle between the element-forming surface of the magnetic head slider, namely, a shield gap layers of the MR element of the magnetic head slider and a radial direction of the lapping plate, is kept in a range equal to or greater than 60 degrees and equal to or less than 80 degrees. Thus, not only a lowering of the resistance of the MR element but also degradation in MR conversion characteristics of the MR element can be prevented. This has been confirmed by experiment.
It is preferred that the lapping step includes lapping the ABS of the bar by relatively moving the lapping plate in a direction crossing the ABS from a side of a surface of the bar, which surface is opposite the element-forming surface, toward a side of the element-forming surface.
It is also preferred that the lapping step includes lapping the ABS of the bar by fixing or varying the angle xcex8 within a range equal to or greater than 60 degrees and equal to or less than 80 degrees.
It is further preferred that the lapping step includes lapping the ABS of the bar by using the lapping plate with diamond abrasive.